In recent years, in processes for assembling and producing various industrial products such as home electronics, and processes for producing devices such as electronic components, batteries and substrates, paste materials that have various functions are coated onto the products or devices, and then, the products or devices are subjected to heat treatments by use of heat treatment apparatuses. For example, the heat treatment apparatuses include drying furnaces, baking furnaces, cure furnaces, and reflow furnaces. Reflow furnaces are used for soldering, for example, in an electronic component-mounting process. Various solvents such as water and organic solvents are mixed into the paste materials in addition to solid contents required in final products, to adjust their viscosities or performance.
Solvents included in paste materials are released therefrom to the inside of heat treatment apparatuses through the vaporization and solvent-removing process in the heating step in the heat treatment apparatuses. If the concentrations of the vaporized solvents inside the heat treatment apparatuses are increased, this possibly causes various problems. For example, if the concentrations of the solvents in the atmospheres inside the heat treatment apparatuses come close to saturation, it may be difficult to dry objects that are subjected to the heat treatments. Therefore, the outside air, or an atmosphere gas such as a nitrogen gas is regularly or continuously supplied into the heat treatment apparatuses, and, simultaneously, the atmospheres that include increased concentrations of the solvents present inside the heat treatment apparatuses are released to the outside.
The solvents included in the released atmospheres can be removed based on, for example, a method disclosed in JP-A-2004-301373, after the atmospheres are discharged from the heat treatment apparatuses. FIG. 7 is a diagram that depicts the system disclosed in JP-A-2004-301373. As shown in FIG. 7, in the disclosed system, a cooler 5, an exhaust duct 6 present outside the heat treatment apparatus 1, and a mist collector 7 are connected in this order to an exhaust duct 4 inside the heat treatment apparatus 1. The cooler 5 cools the exhaust atmosphere discharged from the heat treatment apparatus 1 to thus devolatilize the vaporized solvent included in the exhaust atmosphere. The exhaust atmosphere including the devolatilized solvent is delivered into the mist collector 7 through the exhaust duct 6, and the volatilized solvent is captured and removed in the mist collector 7. Accordingly, the solvent can be removed from the exhaust atmosphere.
FIG. 8 shows another system for removing a vaporized solvent from an exhaust atmosphere. In the system in FIG. 8, discharging electrodes 8 are placed upstream of a direction in which an exhaust atmosphere 122 flows, and dust-collecting electrodes 9 are placed downstream thereof. The exhaust atmosphere 122 passes between the discharging electrodes 8, and between the dust-collecting electrodes 9, in a linear fashion. The discharging electrodes 8 apply electric fields to the exhaust atmosphere 122, and thus, causes the vaporized solvent to charge. The dust-collecting electrodes 9 further apply electric fields to the charged solvent. The solvent to which the electric field has been applied by the dust-collecting electrodes 9 adheres onto the dust-collecting electrodes 9 due to electrostatic attraction. Accordingly, it becomes possible to remove the solvent from the exhaust atmosphere 122.